Objective Some versions of restaurant menu labelling legislation do not require energy information to be posted on menus for drive-through lanes. The present study was designed to quantify the number of customers who purchase fast food through drive-in windows as a means of informing legislative labelling efforts.

Design This was an observational study.

Setting The study took place at two McDonald’s and Burger King restaurants, and single Dairy Queen, Kentucky Fried Chicken, Taco Bell and Wendy’s restaurants.

Subjects The number of customers entering the chain restaurants and purchasing food via the drive-through lane were recorded. A total of 3549 patrons were observed.

Results The percentage of customers who made their purchases at drive-throughs was fifty-seven. The overall average (57 %) is likely a conservative estimate because some fast-food restaurants have late-night hours when only the drive-throughs are open.

Conclusions Since nearly six in ten customers purchase food via the drive-through lanes, menu labelling legislation should mandate the inclusion of menu labels on drive-through menu boards to maximise the impact of this public health intervention.